Reflectance spectrum
Target presets
A preset sets the spectral range, the target bands, the materials, the starting layer and the limits. Edit anything afterwards on the Target tab or in the sidebar.
Incidence
Tolerances
The tolerances are the acceptance criterion: the synthesis stops when |R − R̃| ≤ ΔR and |GDD − G̃| ≤ ΔG at every point of the optimization grid and of the dense check grid. In the merit they are the scales of the two residuals, F = ⟨((R − R̃)/ΔR)²⟩ + ⟨((GDD − G̃)/ΔG)²⟩ — the optimization always pulls both characteristics towards their targets, whatever the tolerances; a smaller ΔG weights the dispersion more against R.
Spectral range
Spectral points closer than half the zone width to a target jump get zero weight: an ideal edge cannot be matched and would otherwise dominate the merit.
Target reflectance bands
Edit the values here, or on the chart: drag a level or a boundary, double‑click a band to split it, double‑click a boundary to merge.
Target Rp bands
The p‑polarization has its own target (the magenta band with a dashed edge on the chart; the Rs band is blue‑green); it shares the spectral range with the Rs target.
Target GDD bands
Group‑delay dispersion on reflection, fs² (negative for a compressing mirror): piecewise‑constant bands on the shared spectral range, shown on the lower panel of the chart as the target G̃ with its tolerance band ± ΔG and edited there like the reflectance target — drag the centre of a band or a boundary, double‑click to split or merge.
Integral targets
An integral target asks for a value of ∫W·C dλ over a range — C the reflectance, transmittance, back‑side reflectance or GDD, W = 1 or the light source × detector (Advanced) — within a tolerance: what the detector receives from the source through the coating. It adds to the merit and to the stop criterion; the spectral target above stays as it is.
Color targets
A color target asks the color of R, T or BR (the light reflected from the back side) — under the illuminant and the observer chosen in Advanced — for given coordinates in L*a*b*, xyY or u'v'Y within a tolerance (ΔE, or a chromaticity distance and a luminance tolerance). It adds to the merit and to the stop criterion; the spectral target above stays as it is. Pick the color on the Color tab, from a palette or with the picker.
Field targets
A field target asks the squared electric field |E|² — in percent of the incident intensity — in a region of the coating (the layers of one material, all layers, the top layers or the surface) at a wavelength or a band, an angle and a polarization to stay under a limit (Minimize), over it (Maximize) or at a value (Target) within Δ|E|² — the tolerance, and the scale of the field in the merit. 100 % is the incident wave alone (the normalized intensity |E|²/|E₀|² = 1). It adds the term F_field to the merit and the condition to the stop criterion; the spectral target above stays as it is. The field is drawn on the Coating structure card (E‑field).